This invention relates to soluble, film-forming polyimides and their copolymers made using 3,5-diaminobenzotrifluoride, and, more particularly, to low dielectric constant, high thermal stability, high Tg, partially soluble, lower moisture uptake, relatively colorless polyimides and their copolymers made using 3,5-diaminobenzotrifluoride and a compound selected from the group consisting of aromatic dianhydrides and their corresponding esters and acids.
Aromatic polyimides have found extensive use in industry as composites, molded parts and dielectrics due to their toughness, flexibility, mechanical strength, high thermal stability, their lower dielectric constant, and high electrical resistivity. Such polyimides have been used in both film and coating form as advanced materials for such uses as passivation and insulating coatings, interlevel dielectrics, die attach adhesives, flexible circuit substrates, and the like.
Although current polyimides have the toughness, flexibility and thermal stability necessary to meet the rigorous processing and operating conditions required for certain uses, they do not exhibit the low dielectric constant and reduced moisture uptake shown by lower thermal stability polymers such as polyethylene and polytetrafluoroethylene. The latter polymers, however, are not useful despite their excellent dielectric and moisture uptake properties if the thermal stability requirements are demanding. In addition, polyimides are generally insoluble even in solvents like N-methyl pyrrolidone or dimethylacetamide which inhibits their usefulness in important areas. In addition, polyimides generally do not form colorless films even when film thickness is below about one mil.
Now it has been found that improved polyimides and copolyimides exhibiting most if not all of the above requirements can be found in the group of polyimides or copolyimides made using 3,5-diaminobenzotrifluoride.